HOUSTON - Marking the second week working together, the Expedition 15 crew wrapped up a week of various maintenance tasks, science experiments and preparations for the May 15 arrival of the Progress 25 supply ship.

To prepare for the new unpiloted cargo carrier's arrival, the currently docked Progress' engines were used to reboost the station Saturday. The move increases the number of rendezvous opportunities for the STS-117 space shuttle mission targeted for next month. Expedition 15 Commander Fyodor Yurchikhin and flight engineers Oleg Kotov and Suni Williams also removed the docking mechanism from the Progress 24 for later use.

The week included work on a wide array of science experiments. Williams completed the fifth run of the Elastic Memory Composite Hinge experiment. The experiment studies the performance of a new hinge composite in space.

Williams also did a test run of a handheld device for rapid detection of biological and chemical substances on board the station. This study is meant to provide an early warning system to protect the health and safety of station crew members. Williams also completed annual re-certification of the Microgravity Science Glovebox and performed a checkout of the cardiac defibrillator.

Kotov did maintenance work in the Zarya module and tested the circuits of a temperature sensor on one of the batteries. He also conducted the periodic collection of air readings in the station with the Russian Real-Time Harmful Contaminant Gas Analyzer system.

Other hardware and maintenance tasks included the replacement of a Common Cabin Air Analyzer, sound level monitoring in the Russian Service Module and in the U.S. Destiny Laboratory, and charging U.S. spacesuits batteries.

Crew members wrapped up the week replacing a heat exchanger in the Zvezda Service Module. They also swapped out computers used in the U.S. lab racks.

The weekend will consist of mostly off-duty time with routine housekeeping, family conferences and a HAM radio session.